A flat panel display device, such as a liquid crystal display device, includes a thin-film-transistor circuit array substrate. Such a thin-film-transistor circuit array substrate is provided with an insulation substrate and pixels formed on the insulation substrate in a matrix. Each pixel contains an arrangement for a pixel electrode, a capacitor and a thin-film-transistor.
The thin-film transistor is made of an island-like poly-silicon film formed on the substrate. The thin-film transistor and the island-like poly-silicon film are coated with a gate insulation film on which, in turn, a gate electrode and a scanning line are deposited. Further, an auxiliary capacitor line is formed on the gate insulation film as a common capacitor line but is separated from the scanning line.
The scanning and auxiliary capacitor lines are covered with an interlayer insulation film. Signal lines are formed on the interlayer insulation film through which contact holes are made to electrically connect the poly-silicon film to the signal lines
The liquid crystal display device further includes a counter substrate containing a color filter insulation layer. The counter substrate is provided opposite to the circuit array substrate. Liquid crystal is put into a gap defined between the circuit array and counter substrates. The gap is then sealed at its circumferences. Such a prior art liquid crystal display device as set forth above is disclosed in Japanese Unexamined Publication No. 2000-187248, its pages 4–6 and FIGS. 1–3.
The prior art liquid crystal display device requires a tremendous number of pixels to display a big volume of data. Particularly, in the case that the liquid crystal display device used for an R, G and B color display PC, its circuit array substrate is necessarily provided with a several millions of pixels.
Recently, a liquid crystal display device has had highly advanced display criteria of which point defects due to incomplete pixels are require to be as few as possible. It is extremely difficult to manufacture a liquid crystal display device with no point defects at a sufficient yield rate. Thus, it is important to provide a liquid crystal display device with a structure of less point defects or a method of manufacturing the same.
One of the prime causes for a point defect pixel is the occurrence of electrostatic-field breakdowns or destruction in manufacturing a circuit array substrate used for a liquid crystal display device. When a patterned poly-silicon film used for thin-film transistors, scanning lines and auxiliary capacitor lines are formed on an insulation substrate, a gate insulation film is provided between the poly-silicon film and the scanning lines.
Subsequently, a plasma chemical vapor deposition (plasma CVD) method is applied by a plasma CVD machine to deposit and form an interlayer insulation film on the scanning lines and the gate insulation film. During the period of depositing the interlayer insulation film or transferring it to somewhere else, electrostatic fields are generated which destroy thin-film transistors.